PN junctions and diodes

In a simple voltage regulator using a Zener diode, what is the role of the resistor placed in series with the diode?

  1. ATo limit the current through the diode and take up the difference between input and output voltage
  2. BTo amplify the signal
  3. CTo convert AC to DC
Show answer and explanation

Answer: A. To limit the current through the diode and take up the difference between input and output voltage

A Zener diode keeps a nearly constant voltage in breakdown even as current changes, but without current limiting it would be destroyed by excess current. The series resistor limits the current and absorbs input voltage variations as a voltage drop, so the output voltage stays nearly constant.

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